Field of the Invention
The present invention relates to an electrophotographic image forming apparatus.
Description of the Related Art
An image forming apparatus that forms an image on a recording material by transferring an image formed on an image bearing member to a recording material in a transfer portion has been proposed. In such an image forming apparatus, the image formed on the image bearing member is conveyed in synchronization with timing at which a recording material reaches the transfer portion. The recording material is temporarily stopped by a registration roller before being conveyed to the transfer portion and is again conveyed in synchronization with the image formed on the image bearing member. Thus, the image can be transferred while the image and the recording material are aligned with each other.
In this manner, if the recording material is stopped temporarily by the registration roller, time necessary for the conveyance of the recording material is increased accordingly and, therefore, productivity (throughput) is reduced. Then, Japanese Patent Laid-Open No. 2008-287236 discloses a method for aligning a recording material and an image formed on an image bearing member without temporarily stopping the recording material by a registration roller. In particular, it is disclosed to perform acceleration and deceleration of the recording material so as to synchronize timing at which an image on an image bearing member reaches a transfer portion and timing at which a recording material reaches the transfer portion in accordance with time after the recording material is fed until a front end of the recording material is detected by a registration sensor.
By conveying the recording material to the transfer portion without temporarily stopping, not as in the related art, a sheet interval between a preceding sheet and a subsequent sheet can be shortened, and productivity can be improved. As another viewpoint of control in feeding the recording material, since recording materials with a high coefficient of friction, such as glossy paper (gross paper), have features that multi feeding are easy to occur, occurrence of multi feeding can be reduced by feeding at a lower sheet feeding speed. However, if the sheet feeding speed is lowered, time necessary to convey the recording material becomes longer. Then, it is considered to reduce a decrease in productivity by setting sheet feeding start timing earlier in a case in which the sheet feeding speed is lowered.
However, in order to set the sheet feeding start timing earlier, it is necessary to provide an image interval between an image formed on a preceding sheet and an image formed on a subsequent sheet so that the subsequent sheet does not contact the preceding sheet due to the earlier sheet feeding start timing of the subsequent sheet. It is possible to provide an enough sheet interval with which the subsequent sheet does not contact the preceding sheet by increasing an image interval to provide the image interval. However, there is a possibility that the sheet interval that has been shortened by conveying the recording material to the transfer portion without temporarily stopping, not as in the related art, should be increased, which causes a decrease in productivity.